1. Field of the Invention
The present invention relates to couplings and more particularly to splined couplings for transmission of torque.
2. Description of the Prior Art
It is common in the field of torque transmission to utilize splined joints to allow extension or compression of the length of a shaft transmitting torque between two components. Such splined joints usually consist of an externally splined male component and an internally splined female component. These components are assembled in the typical fashion.
Looseness or backlash in such joints can be detrimental to the proper and efficient function of the assembly in efficiently transmitting torque between driving and driven components.
In order to minimize backlash between the mating splined components, clearance between the spacing between the splines in the female component and thickness of the teeth of the male component is maintained at a minimum. Concentricity between the two splined components of such an assembly is important. Contrary to the backlash consideration and minimization, reasonable manufacturing capability is typically not considered in the associated manufacturing specifications.
The most cost effective methods in the manufacturing process for volume production of high strength female splined components, include broaching and cold forming. While both of these processes are capable of producing such components with required tolerances on the spacing of the splines and the width of the splines, neither of the processes is effective at maintaining tight tolerances for the major or minor diameter fitting of associated components. This is primarily caused by the elastic properties of the metals used in the formation of these components, and to the internal stresses in the workpiece material. In broaching, the workpiece is oftentimes temporarily deformed due to the pressure exerted on it by the cutting tool. Accordingly, the cutting of the metal of the workpiece is not in its free, undistorted state. When the pressure is released at the end of the cutting operation, the workpiece returns to its free state form and the spline feature of the workpiece varies from its optimum geometry.
In cold forming the material of the workpiece tends to spring back,from the optimum shape after the forming pressure is released.
Large changes in the shape of the workpiece, both in the broaching and cold forming processes can result in unstable dimensional integrity of the workpiece. Residual stresses can be left in the workpiece due to previous mechanical or thermal processing. This causes non-uniform strength properties which can result in a workpiece being distorted to an out-of-round condition. Frequently, the distortion in the roundness of these workpieces exceeds the total permitted tolerance variation.
It is an object of the present invention to produce an internally splined component and a method of making the same wherein the splined components are provided with small cross-section ribs machined to tight tolerances.
Another object of the invention is to produce a splined component having a rib formed on the spline to achieve close tolerances.